Transcript Trade Studies Module - Space Systems Engineering

Trade Studies Module
Space Systems Engineering, version 1.0
Space Systems Engineering: Trade Studies Module
Module Purpose: Trade Studies
 Describe the typical trade study process and show
an example.
 Recognize that trade studies support decision
making throughout the project lifecycle.
 Provide some trade study heuristics to improve the
application and value of future trade studies.
 Describe and provide a trade tree - an option
management graphic.
Space Systems Engineering: Trade Studies Module
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What is a Trade Study?
 A trade study (or trade-off study) is a formal tool that supports
decision making.
 A trade study is an objective comparison with respect to
performance, cost, schedule, risk, and all other reasonable
criteria of all realistic alternative requirements; architectures;
baselines; or design, verification, manufacturing, deployment,
training, operations, support, or disposal approaches.
 A trade study documents the requirements, assumptions,
criteria and priorities used for a decision. This is useful since
new information frequently arises and decisions are reevaluated.
Space Systems Engineering: Trade Studies Module
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Trade Studies Support Decision Making
Throughout the Development Lifecycle
Trade studies support:
• Requirements development - e.g., to resolve conflicts; to
resolve TBDs and TBRs
• Functional allocations - e.g., system architecture
development
• System synthesis - e.g., assess the impact of alternative
performance or resource allocations
• Investigate alternate technologies for risk or cost reduction
• Assess proposed design changes
• Make/buy decisions (i.e., build the part from a new design or
buy from commercial, existing sources)
Space Systems Engineering: Trade Studies Module
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The Trade Study Process (1/2)
1. Define the objectives of the trade study
2. Review inputs, including the constraints and assumptions
3. Choose the evaluation criteria and their relative importance
(these can be qualitative)
4. Identify and select the alternatives
5. Assess the performance of each option for each criteria
6. Compare the results and choose an option
7. Document the trade study process and its results
Space Systems Engineering: Trade Studies Module
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The Trade Study Process (2/2)
Space Systems Engineering: Trade Studies Module
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Evaluation Criteria — Measures (1/2)

Trade studies depend upon having criteria for making
decisions based on measures of effectiveness (voice of the
customer) and measures of performance (voice of the
engineer).

Measure of Effectiveness (MOE) - A measure of how well
mission objectives are achieved. MOEs are implementation
independent - they assess ‘how well’ not ‘how’.

Example measures of effectiveness include
•
•
•
•
•
Life cycle cost
Schedule, e.g., development time, mission duration
Technology readiness level (maturity of concept/hardware)
Crew capacity
Payload Mass
Space Systems Engineering: Trade Studies Module
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Evaluation Criteria — Measures (2/2)
 Measure of Performance (MOP) - A quantitative measure that,
when met by the design solution, will help ensure that an MOE
for a product or system will be satisfied. There are generally two
or more measures of performance for each MOE.
 Example measures of performance
• Mass
• Power consumption
• Specific impulse
• Consumables required
• Propellant type
 Both MOEs and MOPs are system figures of merit; an MOE
refers to the effectiveness of a solution and an MOP is a
measure of a particular design.
Space Systems Engineering: Trade Studies Module
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Trade Study Heuristics
1.
Rules of Thumb:
 Manage the number of options under consideration
 Revisit the original problem statement
 If a baseline solution is established, use it as a ‘yardstick’ to measure
the alternatives.
2.
Decisions are frequently made with imperfect information.
1. Do not get stuck in ‘analysis paralysis’.
2. Decide how deep the analysis must go. {Deep enough to make a
decision with confidence, but no deeper.}
3.
Does the decision feel right? If not, why?
4.
Conduct further what-if scenarios by changing assumptions.
5.
Reject alternatives that do not meet an essential requirement.
6.
Ignore evaluation criteria that do not discriminate between
alternatives.
7.
Trades are usually subjective; numeric results usually give a false
sense of accuracy.
8.
If an apparent preferred option is not decisively superior, further
analysis is warranted.
Space Systems Engineering: Trade Studies Module
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Example Decision Matrix Trade Study
Preferred Solution
Space Systems Engineering: Trade Studies Module
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Example Qualitative Decision Matrix
For a Lunar Thermal Control Trade Study
Characteristics
Single Phase Fluid
Two Phase Fluid
Heat Pipe
Safety: (3)
Operating
Pressure
Low
High
Low-Medium
Safety:
Toxicity
Fluid Dependent
Fluid Dependent
Fluid Dependent
Safety:
Flammability
Fluid Dependent
Fluid Dependent
Fluid Dependent
Reliability (1)
High
Fair
Fair
Performance: (2)
Pumping Cost
Low
High
Fair
Complexity: (4)
Controls
Simple
Nominal
Complex
Complexity: (5)
Simple
Manufacturing
Difficulty
Space Systems Engineering: Trade Studies Module
Nominal
Complex
11
Do A Reality Check On The Tentative Selection
Key questions to ask:

Have the requirements and constraints truly been met?

Is the tentative selection heavily dependent on a particular set of
input values and assumptions, or does it hold up under a range
of reasonable input values (i.e., is it ‘robust’)?

Are there sufficient data to back up the tentative selection?

Are the measurement methods sufficiently discriminating to be
sure that the tentative selection is really better than the
alternatives?
• If close results, is further analysis warranted?

Have the subjective aspects of the problem been fully
addressed?

Test the decision robustness.
• Is the tentative selection very sensitive to an estimated performance
or constraint? If so, explore the full reasonable range of each
performance variable to understand the domain where your
tentative selection is appropriate.
Space Systems Engineering: Trade Studies Module
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Trade Trees
 A trade tree is a graphical method of capturing alternatives
with multiple variables.
 Each layer of the tree represents some aspect of the system
that will be treated in a trade study to determine the best
alternative.
 Some alternatives can be eliminated (or ‘pruned’) a priori
because of technical feasibility, launch vehicle constraints,
cost, risk or some other disqualifying factor.
 The total number of alternatives is given by the number of end
points of the tree.
 Even with just a few layers, the number of alternatives can
increase quickly, so manage their numbers.
Space Systems Engineering: Trade Studies Module
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Decision Package 1
Long vs Short
Conjunction Class
Long Surface Stay
Opposition Class
Short Surface Stay

16 17 18
19 20 21
22 23 24
25 26 27
   
  M1
 M2
M1 M1
Space Systems Engineering: Trade Studies Module

No
ISRU
NTR
Electric
Chemical
13 14 15
ISRU
NTR
Electric
Chemical
10 11 12
ISRU
Propulsive
NTR
Electric
Chemical
NTR
Electric
Chemical
7 8 9
ISRU
Aerocapture
NTR
Electric
Chemical
NTR
Electric
Chemical
4 5 6
ISRU
Propulsive
NTR
Electric
Chemical
ISRU
All-up
NTR
Electric
Chemical
No
ISRU
NTR
Electric
Chemical
No
ISRU
Aerocapture
NTR
Electric
Chemical
No
ISRU
Propulsive
NTR
Electric
Chemical
3
No
ISRU
Aerocapture
NTR
Electric
Chemical
1 2
Propulsive
Pre-Deploy
NTR
Electric
Chemical
NTR
Electric
Chemical
(no hybrids
in Phase 1)
ISRU
All-up
NTR
Electric
Chemical
Aerocapture
Special Case
1-year Round-trip
NTR
Electric
Chemical
Mission
Type
Cargo
Deployment
Human Exploration
Of Mars
Pre-Deploy
Mars Ascent Mars Capture
Propellant
Method
Interplanetary
Propulsion
Top-level Trade Tree-Example for Mars
1988 “Mars Expedition”
1989 “Mars Evolution”
1990 “90-Day Study”
1991 “Synthesis Group”
1995 “DRM 1”
1997 “DRM 3”
1998 “DRM 4”
1999 “Dual Landers”
1989 Zubrin, et.al*
1994-99 Borowski, et.al
2000 SERT (SSP)
2002 NEP Art. Gravity
 2001 DPT/NEXT
M1 2005 MSFC MEPT
M2 2005 MSFC NTP MSA
28 29 30
31 32 33 34 35 36
37 38 39
40 41 42
43 44 45
46 47 48
No
ISRU
M2

M2
ISRU
No
ISRU
ISRU
No
ISRU

M2 M2
NTR- Nuclear Thermal Rocket
Electric= Solar or Nuclear Electric Propulsion
14
Earth-Moon Transit Trade Tree
Outbound
Location
LO
L1 - LO
Destination
Dock
Un-Dock
Inbound
Lunar Surface (LS)
High Priority
Medium Priority
Low Priority
LS
LO - LS
K
Both Dock / Un-Dock
LS - LO
Dock Optional
LO
L
Transportation Functions
LO - L1
EO - L1
L1
2,3
L1 - LS
Element Trades
Earth
Surface
L1
L
EO
L1 - EO
K
K
L
Water
EO - ES
Land
K
1,4&C4,5-8,12
LO - LS
ES - EO
EO
LO
EO - LO
M
M
N
Water
L1 - ES
L
K
LO
LO - EO
9, 13
EO - LS
L1 - LO
ES
N
Water
EO - ES
LO - LS
7,8
Land
K
M
11
M
N
Water
LO - ES
Land
K
ES - L1
EO
L
L1 - LS
Land
N
LS - L1
L
L1
L1
N
L
L1 - EO
1,3-6,10,12
EO
L
Earth Surface
Water
EO - ES
Land
K
M
H = Human Mission Segment
LS - EO
LO - LS
LO
Water
Land
L
M
Orbital Operations &
Earth-Moon Transit;
Propulsion Options
All Chemical
1-4, 7-13 L
Chemical + Electric
5
NTR
6
Other Hybrid
Options
Space Systems Engineering:
Trade
Studies Module
K
C1-3,5-13
N
Water
LS - ES
L
L
Lunar
Descent/Ascent
Lander Options
Integrated Crew
Transit/Lander
Function
Earth EDL Orbit
Capture Options
Low L/D
7
M
Propulsive Capture
8
13
N/A
N
Earth Entry Vehicle
L/D Options
Aerocapture
Modular Elements 1-12
9,13
Land
C
Cargo Mission Segment (Pre-Deployed Surface Cargo)
2,11
EO - ES
L
ES - LS
H
Water
Land
EO
10
M
Human Mission Segment
N
L1 - ES
C = Cargo Mission Segment
ES - LO
M
N
1-11,13
Medium L/D
12
High L/D
N/A
1-6,9-13
15
Example: Earth-Moon Transit Trade
Option Analyses
Outbound
Inbound
Lunar Surface (LS)
LO
L1 - LO
Location
Destination
Dock Optional
LS
LO - LS
K
Transportation Functions
LS - LO
LO
L
Element Trades
LO - L1
EO - L1
L1
Key measure of performance: mass
Earth
Surface
L1
L
L1 - LS
EO
L1 - EO
K
K
Water
L
EO - ES
Land
K
LO - LS
ES - EO
EO
M
M
LO
EO - LO
N
Water
L1 - ES
L
K
Land
LO - EO
EO - LS
N
L
LO
L1 - LO
EO
Water
EO - ES
LO - LS
Land
K
M
M
N
L1 - LS
Water
LO - ES
Land
K
ES
ES - L1
LS - L1
L
L1
L1
N
L
L1 - EO
EO
L
Earth Surface
Water
EO - ES
Land
K
M
M
N
Water
L1 - ES
LS - EO
EO
Land
280
N
Water
LO - LS
EO - ES
LO
ES - LO
Land
L
L
M
M
N
Water
ES - LS
LS - ES
L
Orbital Operations
& Earth-Moon
Transit; Propulsion
Options
All Chemical
Chemical + Electric
NTR
Other Hybrid Options
L
Integrated Crew
Transit/Lander
Function
Modular Elements
Earth EDL Orbit
Capture Options
Low L/D
Aerocapture
N
M
Propulsive Capture
N/A
Land
N
Earth Entry Vehicle
L/D Options
Medium L/D
High L/D
240
N/A
Total Architecture Mass (t)
K
L
Lunar
Descent/Ascent
Lander Options
17
• Ascent/Descent stages for L1 approach are significantly
higher than for LO approach (combination of higher V
and habitat masses).
36
• NTR propulsion applied to TLI function results in
significant IMLEO benefit due to influence of TLI
maneuver.
200
8
160
• TLI stages dominate mass composition.
11
• Single crew module carried through entire mission has
large scaling effect on all propulsive stages.
96
36
15
120
3
16
3
16
6
6
47
47
52
80
Ascent
Descent
TEI
TLI #2
TLI #1
Crew
OM
SH
EV
3
16
96
19
40
0
Space Systems Engineering: Trade Studies Module
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47
47
34
10
3
9
3
9
3
9
3
20
1) DRM
2) Thru LO
3) LO/L1 Hybrid
5b) NTR Thru LO
10b) Single
Module Thru LO
16
Further Considerations
for Trade Studies
and Class Discussion
Based on Observations from
The University of Texas at Austin
Senior Mission Design Class, 2007
(Department of Aerospace Engineering)
Space Systems Engineering: Trade Studies Module
Trade Study Considerations (1/4)
Assumptions
 Trade studies are based on assumptions the team makes.
 Examples of driving assumptions:
• Crew size assumption drives the amount of consumables and the
viability of an open ECLSS versus partially closed ECLSS.
• Mission duration assumption drives the amount of power required
which in turn drives the choice of power subsystem.
• Landing location on the moon drives delta-v requirements which in
turn drives best orbit selection and propulsion subsystem.
 Changing assumptions within the trade study allows the team to
perform a ‘what-if’ analysis.
• Allows the team to understand the integrity of the design alternative
selected
• Shows the importance of that assumption
Space Systems Engineering: Trade Studies Module
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Trade Study Considerations (2/4)
Mission environment
 The trade space for subsystem alternatives is often defined by
the space environment for the mission.
• Why use RTGs when the mission is at 1 AU or on the Moon. When
do we use RTGs? For deep space missions where solar intensity is
less.
• Types of thermal control - need to consider the operating
temperature extremes
• Types of rendezvous and ‘landing’ with a NEO - need to understand
the orbit, spin and known composition of asteroid
• Sometimes the worst of the space environment, such as a solar
particle event (SPE) for radiation, can be avoided by operational
solutions rather than design solutions, i.e., perform the mission
during the minimum of the solar cycle or using early warning
sentinel satellites.
• Lunar missions - is your system operating at one particular location
or region (like Apollo at equatorial latitudes), or at global sites
depending on the particular mission?
Space Systems Engineering: Trade Studies Module
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Trade Study Considerations (3/4)
Importance of information for each alternative
 Trade study analysis should use information that is relevant.
Extraneous information can distract the decision maker.
 ‘Materials’ example:
• Do material characteristics such as tensile strength and Poisson’s
ratio really matter in the selection process.
• In considering so many material alternatives, was heritage
considered as a design factor, i.e, has this material flown on
previous space missions?
• If not, what is the cost to your project for bringing that technology up to
flight-ready status?
• Did you violate one of your original mission scope assumptions of using
current state-of-the-art technology?
• In considering material alternatives, were other correlated factors
included which would shorten the trade space to begin with, such
as material’s impact on radiation protection; use for a pressure
vessel vs. landing struts.
Space Systems Engineering: Trade Studies Module
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Trade Study Considerations (4/4)
Trade study vs. spacecraft design
 Is a trade study really necessary?
• Cargo capsule example:
• Structural design of capsule is not a trade. Evaluation criteria are the
design characteristics; heritage is reference information for actual design
work.
• Seismic vehicle example:
• Two existing concepts versus determining which characteristics are most
valuable for your team design to include
• Mars habitat example:
• What are the communications requirements for the mission (voice, video,
etc) => amount of bandwidth to specify for comm subsystem.
 What makes for a successful mission? Answer defines which
trades are of most importance & might drive additional trades.
• Maximum surface exploration time => robust power and ECLSS
• Precise NEO orbit tracking for X years => tracking method
• 1-week cargo delivery => launch vehicle availability and mission plan
Space Systems Engineering: Trade Studies Module
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Module Summary: Trade Studies
 Trade studies are common decision-support tools that are
used throughout the project lifecycle to capture and help
assess alternatives.
 The steps in the trade study process are:
1.
2.
3.
4.
5.
6.
7.
Define the objectives of the trade study
Review inputs, including the constraints and assumptions
Choose the evaluation criteria and their relative importance
Identify and select the alternatives
Assess the performance of each option for each criteria
Compare the results and choose an option
Document the trade study process and its results
 Trade trees are graphical tools that help manage multivariable options.
Space Systems Engineering: Trade Studies Module
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Back-up Slides
for Trade Studies Module
Space Systems Engineering: Trade Studies Module
Trade Studies

The systems engineering method relies on making design decisions
by the use of trade studies.

Trade studies are necessary when the system is complex and there
is more than one design approach.

Trade studies involve the comparison of alternatives
• Good to explore a number of different alternatives
• Alternatives should be compared at the same level of detail
• Key is for characteristics to be evaluated relative to one another

Trade study approaches:
• Comparing advantages and disadvantages of several alternatives; can
be qualitative.
• Using a formal ranking system based on multiple criteria and a weighting
system; quantitative approach.
Space Systems Engineering: Trade Studies Module
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Example Trade Study Outline
Purpose of Study
• Resolve an Issue
• Perform Decision Analysis
• Perform Analysis of Alternatives (Comparative analysis)
Scope of Study
• State level of detail of study
• State Assumptions
• Identify Influencing requirements & constraints
Trade Study Description
• Describe Trade Studies To Be Performed
• The Studies Planned To Make Tradeoffs Among Concepts, User Requirements, System
Architectures, Design, Program Schedule, Functional, Performance Requirements, And
Life-cycle Costs
• Describe Trade Methodology To Be Selected
• Describe Technical Objectives
• Identify Requirements And Constraints
• Summarize Level of Detail of Analysis
Analytical Approach
• Identify Candidate solutions to be studied/compared
• Measure performance
o Develop models and measurements of merit
o Develop values for viable candidates
• Selection Criteria -- risk, performance, and cost are usually at lease three of the factors
• Scoring
o Measures of results to be compared to criteria
•
Weighted reflecting their relative importance in the selection process
•
Sensitivity Analysis
Trades Results
• Select User/Operational Concept
• Select System Architecture
• Derive Requirements
o Performing trade studies to determine alternative functional approaches to meet requirements
o Alternate Functional Views
o Requirements Allocations
• Derive Technical/Design Solutions
• Cost Analysis Results
• Risk Analysis Results
Space Systems Engineering: Trade Studies Module • Understand Trade Space
25
Decisions to Make Before Beginning a Trade Study
 Has success been defined?
 Which trades need to be done and at what phase of the project?
 For each trade what criteria will be used and what are their
relative weights?
 How deep will the analysis go?
• Deep enough to make a decision with confidence, but no deeper.
 Criteria for doing a trade study?
• The easiest trade study to do is the one that does not have to be
done.
• Do not do a trade study just because you can.
Space Systems Engineering: Trade Studies Module
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Trade Study Process
Define
Evaluation
Criteria/
Weighting
factors
Study Inputs:
 Constraints
 Ops Concept
 Existing
requirements
 Assumptions
 Relevant plans
& documents
Determine
Scope of the
Trade Study
Generate
Viable
Alternative
Solutions
Space Systems Engineering: Trade Studies Module
Evaluate
Alternatives
Against
Criteria
Create
Trade
Tree
Perform
Sensitivity
Analyses
TRADE
STUDY
RESULTS
 Data - graphical
 Recommended
approach
 Benefits
 Resulting risk
posture
 Summary of
results
 Summary of
approach
27
Focused Trade Study
Phase I Analysis
Mass Estimation Benchmark
“Pseudo-Apollo”
Requirements
Baseline Reference
Mission
Design Environments
Subsystem Technologies
Architectural Variations
Parametric Variations
•
2-launch solution
•
Alternate propellants.
•
3-launch solution
•
Alternate power sources.
•
25mt launch constraint
•
Variation in return payload
•
Initial CEV/lander mating in LEO
•
Variation of delivered payload to the lunar surface
•
Single pass aerocapture, deorbit phasing, and capability of
land landing
•
All versus partial crew to the lunar surface
•
Reduce crew size to 2
•
Increase crew size to 6
•
Change in time between launches (7 to 30 days)
•
Reduce lunar surface stay time to 3 days
•
Increase lunar surface stay time to 14 days
•
Effects of elimination of CEV contingency EVA requirement
•
Mass effect of supplemental radiation shielding
Architectural Variation
•
Lunar Orbit Rendezvous of CEV/lander
Space Systems Engineering: Trade Studies Module
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Focused Trade Study Results
Mission Design
Reference Operations Concept
L1-Earth Co-Planar Inbound Delta V Requirement (m/s)
• Moon: Inclination near maximum, Distance near perigee
• L1 Departure Time in June 2006
23/06:00
MOON
22/18:00
22/12:00
8
0
0
22/06:00
22/00:00
21/18:00
21/12:00
21/06:00
21/00:00
Expended
L1 (~322,000
km)
4 weeks
Earth
Departure
Stage
Expended
Earth
Departure
Stage
Expended
20/18:00
Water
Landing
L1 Departure Date (dd/hh:mm)
700-800
Initial Mass in LEO
800-900
900-1000
1000-1100
Service
Module
Expended
LEO 407
km
19/06:00
0
10
0
00
11
00
12
00
13
00
19/00:00
18/18:00
18/12:00
18/06:00
18/00:00
17/18:00
17/12:00
17/06:00
17/00:00
16/18:00
8
0
0
9
Low Lunar
Orbit
Earth Vacuum Perigee Arrival Date
(dd/hh:mm)
23/00:00
9
0
0
Kick Stage
Expended
1100-1200
1200-1300
Continue
CEV
Missions
Reused?
1300-1400
EARTH
320
Total Architecture Mass (kg/1000)
280
240
241
230
216
220
Lander EDS # 1
94
Lander EDS # 1
64
Lander EDS # 1
90
Lander EDS # 1
93
160
Kick Stage
27
40
0
A scent Stg
20
Kick Stage
27
Kick Stage
27
Descent Stg
23
Descent Stg
23
Lander EDS # 1
94
Lander EDS # 3
25
Lander EDS # 4
25
Descent Stg
23
80
240
223
Lander EDS # 2
25
200
120
Lander EDS # 1
25
Lander EDS #1
Lander EDS #2
Lander EDS #3
Lander EDS #4
Kick Stage
Descent Stg
Ascent Stg
CEV EDS #1
CEV EDS #2
CEV SM
CEV CM
Kick Stage
26
Descent Stg
25
Kick Stage
33
Descent Stg
23
A scent Stg
20
A scent Stg
20
142
Kick Stage
27
Lander EDS # 1
42
Descent Stg
23
A scent Stg
20
Descent Stg
13
A scent Stg, 10
A scent Stg
20
A scent Stg
20
CEV EDS # 1
33
CEV EDS # 1
33
CEV SM , 18
CEV SM , 15
CEV SM , 18
CEV SM , 20
CEV SM , 27
CEV SM , 15
CEV SM , 12
CEV CM , 9
CEV CM , 9
CEV CM , 9
CEV CM , 9
CEV CM , 9
CEV CM , 11
CEV CM , 8
BRM
2 Launch
Solution
3 Launch
Solution
25t Launch Limit
Initial Mating in
LEO
Aerocapture &
Land Landing
"Pseudo-Apollo"
CEV EDS # 1
39
CEV EDS # 1
21
CEV EDS # 1
64
CEV EDS # 1
45
CEV EDS # 1
42
CEV EDS # 2
21
Space Systems Engineering: Trade Studies Module
Key Figures of Merit
Safety
Effectiveness
•
•
•
•
•
•
•
•
•
•
# of Critical Events
Mission Complexity
Abort Options
Crew Time
Technology Risk
Probability of launch
success
• Etc.
Total Mass
Dry Mass
Surface Time
Etc.
Extensibility
•
•
•
•
Long-Stays
Mars
Other destinations
Etc.
29
Affordability Trades
Space Systems Engineering: Trade Studies Module
30
Broad Trade Study Overview
 Multi-center team assessed potential mission
concept trade options around two broad Lunar
Mission Scenarios
Outbound
Inbound
Lunar Surface (LS)
LO
L1 - LO
Location
Destination
Dock Optional
LS
LO - LS
K
Transportation Functions
LO
LS - LO
L
Element Trades
L
L1 - LS
Water
L
EO - ES
LO - LS
ES - EO
EO
M
N
M
N
M
LO
EO - LO
Water
L1 - ES
L
K
Land
LO - EO
EO - LS
EO
N
L
LO
L1 - LO
Water
EO - ES
LO - LS
Land
K
M
L1 - LS
Water
LO - ES
Land
L1
LS - L1
L
L1
ES - L1
ES
N
L
L1 - EO
EO
L
Earth Surface
Water
EO - ES
Land
K
M
M
N
Water
L1 - ES
LS - EO
EO
Land
N
Water
LO - LS
EO - ES
LO
ES - LO
Land
L
L
M
M
N
Water
ES - LS
LS - ES
L
Orbital Operations
& Earth-Moon
Transit; Propulsion
Options
L
Lunar
Descent/Ascent
Lander Options
All Chemical
Chemical + Electric
NTR
Other Hybrid Options
K
Earth EDL Orbit
Capture Options
Low L/D
Aerocapture
Integrated Crew
Transit/Lander
Function
L
Land
N
Earth Entry Vehicle
L/D Options
N
M
Medium L/D
Propulsive Capture
High L/D
N/A
N/A
Modular Elements
LMS Trade Tree Definition
Mass (t)
0
50
100
150
200
250
300
350
400
450
1) DRM
4a) Chem + SEP
LMS-1 DRM
IMLEO = 181 t
4c) Chem + NEP
280
5a) Nuclear Thermal
17
• TLI stages dominate mass composition.
L1 Options
6a) Aerocapture
• Ascent/Descent stages for L1 approach are significantly
7a) Propulsive
higher
than forCapture
LO approach (combination of higher V
and habitat masses).
240
Total Architecture Mass (t)
8a) Medium L/D
• NTR propulsion
applied to TLI function results in
9a) ES Direct to L1
significant IMLEO benefit due to influence of TLI
10a) Single Crew Module
maneuver.
200
8
160
large scaling
effect
on all propulsive stages.
3) LO/L1
Hybrid
36
4b) Chem + SEP
15
4d) Chem + NEP
3
5b) Nuclear Thermal
16
6b) Aerocapture
6
120
52
25%96IMLEO
difference
3
16
Lunar
6
7b) Propulsive Capture
478b) Medium L/D
80
47
IMLEO Dry
IMLEO Gross
47
Note: All options
assume 3 crew
modules
unless otherwise
indicated.
96
19
10b) Single Crew Module
52
Ascent
Descent
TEI
TLI #2
TLI #1
Crew
Orbit
Options
OM
SH
EV
3
16
9b) ES Direct to LO
40
36
LO Variant of DRM
IMLEO
11 = 136 t
2)• Lunar
Orbit
Variant
of DRM
Single
crew
module
carried through entire mission has
47
34
0
10
3
9
3
9
3
9
3
20
1) DRM
2) Thru LO
3) LO/L1 Hybrid
5b) NTR Thru LO
10b) Single
Module Thru LO
Trade Option Analyses
 Analysis of numerous trades and options
conducted
LMS-1, TO 2 - Propellant Trade
Percent Increase of IMLEO (%)
100
250
230
210
IMLEO (t)
• LMS-1: 10 trade options + alternatives
• LMS-2: 13 trade options + alternatives
Land
K
• LMS-1 - global access, 7-day surface stays
• LMS-2 - south pole access, 30-90 day surface stays
• Establish data/rationale for potentially infeasible
mission concepts
• Provide focus on trade options to be analyzed in
more detail
EO
L1 - EO
K
K
K
 Screening of breakthrough technologies
conducted for applicability to Spirals 1 and 2
 Trade tree defined for each LMS served as the
basis for trade option identification
 Initial down-selection of major trade tree branches
was performed to:
Earth
Surface
L1
LO - L1
L1
EO - L1
190
170
90
80
70
60
50
40
30
20
10% decrease
in Lander PMF results in
10
12% increase in IMLEO
150
0
Ascent Only
130
110
90
-25%
Storables
LOX/RP1
LOX/Methane
Ascent + Descent
Ascent + Descent +
TEI
All Stages
Note - Percent Increase of IMLEO compared to Baseline (All LOX/LH2)
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
25%
% change
Space Systems Engineering: Trade Studies Module
Sensitivity Analyses
31
Example: Trade Option Analyses
Outbound
Inbound
Lunar Surface (LS)
LO
L1 - LO
Location
Destination
Dock Optional
LS
LO - LS
K
Transportation Functions
LS - LO
LO
L
Element Trades
LO - L1
EO - L1
L1
Earth
Surface
L1
L
L1 - LS
EO
L1 - EO
K
K
Water
L
EO - ES
Land
K
LO - LS
ES - EO
EO
M
M
LO
EO - LO
N
Water
L1 - ES
L
K
Land
LO - EO
EO - LS
N
L
LO
L1 - LO
EO
Water
EO - ES
LO - LS
Land
K
M
M
N
L1 - LS
Water
LO - ES
Land
K
ES
ES - L1
LS - L1
L
L1
L1
N
L
L1 - EO
EO
L
Earth Surface
Water
EO - ES
Land
K
M
M
N
Water
L1 - ES
LS - EO
EO
Land
N
Water
LO - LS
EO - ES
LO
ES - LO
Land
L
L
M
M
N
Water
ES - LS
LS - ES
L
Orbital Operations
& Earth-Moon
Transit; Propulsion
Options
K
All Chemical
Chemical + Electric
NTR
Other Hybrid Options
L
Lunar
Descent/Ascent
Lander Options
L
Integrated Crew
Transit/Lander
Function
Modular Elements
Earth EDL Orbit
Capture Options
Land
N
Earth Entry Vehicle
L/D Options
LMS-1, TO 2 - Propellant Trade
Low L/D
Aerocapture
N
M
Propulsive Capture
Medium L/D
High L/D
N/A
N/A
Percent Increase of IMLEO (%)
100
90
80
Storables
LOX/RP1
LOX/Methane
70
60
50
40
30
20
10
0
Ascent Only
Ascent + Descent
Ascent + Descent +
TEI
All Stages
Note - Percent Increase of IMLEO compared to Baseline (All LOX/LH2)
Space Systems Engineering: Trade Studies Module
32
ECLSS Design Options for a Lunar Rover
Design Factor
Option 1
Option 2
Option 3
Recovery
Open
Partially Closed
Totally Closed
Consumables
Non-regenerate
Base regenerate
Vehicle regenerate
O2
Carry all
Carry all
Carry part; recover
part from CO2 &
H2O
CO2
Absorb, dump
Absorb, carry
back to base
Regenerate in
vehicle
H2O
Absorb, dump
Condense and
carry back or
sublimate
Electrolysis in
vehicle
Cooling
Sublimator
Sublimator
Radiator
Losses
O2 & H2O
Only lose water
Nothing
for cooling by
sublimator; O2 is
recovered at base
Space Systems Engineering: Trade Studies Module
33